Method and apparatus for anchoring hardwood floor systems

ABSTRACT

A standoff sleeve/fastener assembly and a powered driver are provided for anchoring a subfloor component of a hard wood floor system to a concrete slab. The sleeve has a peripheral flange and a countersink at a first end. The fastener is disposed in the sleeve and has an enlarged head that is adjacent to but spaced from the first end of the sleeve. The driver has a nozzle with a striker bore sized to receive the head of the fastener and a recess sized to accommodate the peripheral flange of the sleeve. The subfloor component is anchored by (1) positioning the sleeve/fastener assembly in a hole in that component with the bottom end of the sleeve contacting the concrete slab, (2) positioning the driver nozzle so that the fastener head and the flange of the sleeve reside in its striker bore and recess respectively, and (3) operating the driver whereby its striker impels the fastener to (a) pierce and penetrate the concrete slab and (b) lock the sleeve between the concrete slab and the head of the fastener.

FIELD OF THE INVENTION

[0001] This invention relates to hardwood floor systems and moreparticularly to an improved method and apparatus for anchoring suchsystems to a base made of concrete or like material.

BACKGROUND OF THE INVENTION

[0002] Hardwood floor systems used for sports, such as basketball,require a significant degree of cushioning or impact absorption of thefloor relative to the underlying base to which it is secured in order toreduce injuries. Accordingly a number of different floor systems havebeen designed to provide an appropriate amount of floor deflection andresiliency. Such floor systems include a plurality of hardwoodfloorboards, one or more subfloor layers supporting the floorboards, anda plurality of elastomeric pads attached to and underlying the subfloorlayer(s) for supporting the floor system on a base in the form of aconcrete or asphalt slab. In, some cases, the base may be a pre-existingwood floor. The floor system is anchored to the base by metal fastenersin such a way as not to precompress the elastomeric pads when the floorsystem is in an unloaded state, thereby leaving a gap of free spacebetween the subfloor(s) and the base with the vertical dimension of thatspace being such as to allow downward deflection of the floor underimpact, thereby providing shock absorption and resiliency or give, andreducing the amount of reaction force imparted by the floor system tothe impacting person or object.

[0003] The free space provided between the subfloor layers and the baseis also important with respect to reducing the effect of humiditychanges on the dimensional stability of the wood components. Woodcomponents are susceptible to absorption or expulsion of moisture, witha resultant expansion or contraction. The effect of humidity changes onthe dimensional stability of the floor system is reduced by the freespace since the latter limits moisture transfer between the base and thesupported components.

[0004] A number of different floor systems are known that are designedto provide some degree of impact absorption and are characterized byfree space between the base and the subfloor layers. One of thosesystems is disclosed in U.S. Pat. No. RE37,615, issued Apr. 2, 2002 toMichael W. Niese for “Anchored/Resilient Hardwood Floor System”. Thedisclosure of that patent is incorporated here by reference.

[0005] In the construction disclosed and claimed in U.S. Pat. No.RE37,615, a plurality of mutually spaced sleepers in the form ofelongated nailing members are used to form a subfloor layer forsupporting a layer of hard wood floorboards that serve as the wearsurface. One or more subfloor layers are interposed between the sleepersand the hardwood wear surface. The sleepers also include compressiblesupporting pads, e.g., pads made of a suitable elastomer. In the floorsystem disclosed in the aforesaid patent, a fastening arrangement isused to secure the sleepers directly to the base so that (a) the padsare not precompressed, i.e., the pads are not compressed beyond thecompression that results solely from the weight of the flooring systemcomponents carried by the pads, and (b) the sleepers can deflectdownwardly upon impact to the upper layer of the floor system but arerestricted against upward movement beyond the initial static position ofthe pads. The fastening arrangement includes counterbored holes in thesleepers, floor-anchoring fasteners that extend through the counterboredholes into the base, and means for limiting the depth of penetration ofthe fasteners into the base so that the downward driving forces appliedvia the fasteners do not precompress the elastomer pads. Further detailsof such a system are presented hereinafter in connection with FIG. 1.

[0006] Floor systems similar to the type claimed of U.S. Pat. No.RE37,615 are in commercial use. The foregoing patent indicates that thefloor system disclosed therein may be anchored by forcing fasteners intopredrilled holes in the base or by driving fasteners into the base usinga nail gun without any pre-drilled holes. However, as a practical matterprior to this invention it was not feasible or practical to anchor thesleepers to a concrete base without first predrilling holes for thefasteners in the concrete. Instead the usual practice has been topredrill holes in the concrete base and use fasteners that arecharacterized by a shoulder that function as a depth stop and anexpansion curve adjacent their leading end for anchoring the fastenersin the concrete base, with the fasteners being surrounded by plasticlubricating sleeves that sit loosely in the counterbored holes and serveto reduce friction between the fasteners and the sleepers, asillustrated in FIG. 9 of U.S. Pat. No. RE37,615. Typically thelubricating sleeve has a peripheral flange at its top end and the flangeportion has a counterbore to accommodate the head the fastener. Thefasteners are driven into the predrilled holes by manually impactingthem with a hammer.

[0007] Manually driving a fastener into dense concrete withoutpredrilling a hole to accommodate the fastener cannot be done at all, orat least not without having to strike each fastener repeatedly. However,the holding power of a fastener driven into solid concrete by repeatedblows is poor. If a fastener is impacted with sufficient force topenetrate a concrete substrate, a so-called “ball” is formed in theconcrete around the leading end of the fastener. That ball is adensification of the concrete and it exerts a tight grip on thefastener. However, if thereafter the embedded fastener is impacted oneor more times, the ball will be disrupted and even disintegrate, withthe result that the concrete's grip on the fastener is weakenedsubstantially. It is well known in the structural fastening field thatthe same phenomenon occurs when impact driving a fastener into a steelsubstrate. Therefore, to maximize the holding power, a fastener shouldnot be hit more than once when impact driven into concrete or steel.

[0008] Heretofore powered impact-type drivers have been used for drivingfasteners into concrete or other hard masonry substrates for the purposeof anchoring metal components to the substrates. However, prior to thisinvention use of power drivers for anchoring the sleepers disclosed U.S.Pat. No. RE37,615 was not feasible. The primary problem stems from -thecounterbored holes in the sleepers. The counterbores are designed toaccommodate the heads of the fasteners so they will not protrude abovethe sleepers where they can interfere with the underfloor memberscarried by the sleepers, particularly when the floor system is deflecteddownwardly under impact.

[0009] In the case where lubricating sleeves with peripheral flanges attheir top ends are used with the fasteners, the counterbores also serveto provide a recessed seat for the flanges. However, the requirementthat the heads of the fasteners (and also the flanges of the lubricatingsleeves when used) be recessed in the counterbores has made it difficultto use a power driver. The need to recess the heads of the fasteners inthe counterbores complicates attainment of the requirement that thestriker or hammer of the power driver be able to drive the fastenersdeep enough to assure a tight engagement of the fastener heads (or theflanges of the lubricating sleeves) with the bottoms of thecounterbores, but not so deep as to preload the resilient pads. Thecounterbored holes also make it difficult to center the striker orhammer of the powered driver on the fastener head, which is an importantconsideration since optimum performance of the driver requires that itsstriker be readily centered on the fastener head and the driver bepositioned to drive the fastener perpendicularly to the base. Thiscentering problem is complicated by the fact that in actual practice thelubricating sleeves are sized to make a loose fit in the counterboredholes. Another factor discouraging against use of a power driver is therequirement that the action of the driver must not interfere with theuse of fastener depth stop means designed to prevent compression of theresilient pads, as those disclosed in U.S. Pat. No. RE37,615.

[0010] Because of these problems there has been lacking a satisfactoryand reliable way to secure the sleepers of the form disclosed in saidpatent to a concrete base without using pre-drilled holes for thefasteners. The need to predrill holes introduces a variety oflimitations, the most significant of which is that installation of suchsystems is slow and costly due to the manual labor consumed inpredrilling holes in the concrete and the need to precisely locate theholes to assure alignment with the counterbored holes in the sleepers,and the repeated hammering action required to seat the fastener.

OBJECTS AND SUMMARY OF THE INVENTION

[0011] The primary object of this invention is to provide a method andmeans for anchoring a hardwood floor system to a concrete base withfasteners without the need for predrilling holes for the fasteners.

[0012] A more specific object is to provide an improved method and meansfor anchoring floor system sleepers of the type that have counterboredholes to accommodate fasteners for anchoring the sleepers to a concretebase.

[0013] Another object is to provide a novel and improved fastenerarrangement for anchoring hardwood floor systems.

[0014] Still another object is to provide a power driver that is adaptedfor driving fasteners to anchor sleepers that have counterbored holesfor the fasteners.

[0015] A further object is to provide a novel and improved fastenerarrangement comprising a fastener and a hard plastic standoff sleeve forthe fastener that is adapted to withstand fracture by the fastener whenthe fastener is impacted by the striker of a power driver.

[0016] The foregoing and other objects of the invention are achieved byproviding a standoff sleeve/fastener arrangement for anchoring a sleeperof the type described to a concrete base, and a power driver for drivingthe fastener into the concrete base. The standoff sleeves are sized tofit loosely (approximately {fraction (1/32)}″ to {fraction (1/16)}″clearance in counterbored holes preformed in the sleeper. Each sleevehas a center bore for accommodating the shank of the fastener and aperipheral flange at its top end that is sized to fit within thecounterbore. Also in relation to the associated fastener the sleeve hasan effective length that enables it to function as a depth stop thatprevents the fastener from pre-compressing the resilient pads of thesleeper. Each fastener has a radially projecting head at its top end,with the head having a tapered side surface and the sleeve having acountersink for accommodating the fastener head. In a preferredembodiment of the invention, the taper angles of the side surface of thefastener head and the countersink being are set so that when the head isdriven into engagement with the top end of the sleeve, the impact forcewill be transmitted progressively to the sleeve from the fastener, withthe radial and axial vectors of the impact force decreasing andincreasing respectively with increasing penetration of the fastener. Thefasteners are driven into the concrete base by means of a power driverthat has a nozzle sized to fit within the counterbores of the holes inthe sleeper and a striker bore that is sized to accept the head of afastener disposed in one of the counterbored holes, whereby the strikerof the driver will be aligned with the head of the fastener and the toolwill be oriented perpendicularly to the sleeper, as required for optimumdriving of the fastener into concrete. The standoff sleeves function asa depth stop to prevent or limit preloading of the resilient pads on thebottom of the sleeper by the driven fasteners. Preferably but notnecessarily, the drive stroke of the driver's striker is limited so asto permit it to drive the fastener to a depth that is sufficient tosecure the sleeper to the concrete base but not so far as to overloadthe resilient pads or damage the sleeve. Other features and advantagesof the invention are set forth in or rendered obvious by the followingdetailed description which is to be considered together with thedrawings.

THE DRAWINGS

[0017]FIG. 1 is a cross-sectional view in elevation of a sleeper-typeflooring system;

[0018]FIG. 2 is a fragmentary side view in elevation of the same floorsystem;

[0019]FIG. 3 is a fragmentary plan view taken along line 3-3 of FIG. 1;

[0020]FIG. 4 is a an exploded view in elevation, partly in section, of apreferred form of fastener and sleeve provided according to the presentinvention;

[0021]FIG. 5 is a fragmentary sectional view illustrating a sleeve andfastener in ready position for a fastening operation;

[0022]FIG. 6 is a view similar to FIG. 5 showing a fastener near the endof its travel into a concrete base;

[0023]FIG. 7 is a side view in elevation of a powered driver modifiedfor use in practicing the invention;

[0024]FIG. 8 is a fragmentary elevational view, partly in section,illustrating the nozzle portion of the powered driver of FIG. 7 inexploded relation to a fastener and sleeve used for anchoring a floorsystem according to the invention; and

[0025]FIG. 9 illustrates another type of floor system with which theinvention may be used.

DETAILED DESCRIPTION OF THE INVENTION

[0026] FIGS. 1-3 illustrate a section of a floor system of the typedisclosed in U.S. Pat. No. RE37,615. The floor system comprises aplurality of mutually spaced attachment members in the form of woodensleepers 2 having resilient pads 4 on their bottom side and supportingat least one subfloor layer 6 on their top side. The sleepers areanchored to and supported by a base 8 formed of concrete. Overlying thesubfloor layer 6 is a hard wood floor 10 which usually is made up ofinterlocked tongue and groove maple floorboards. The subfloor layer(s)may take various forms, e.g., as disclosed in U.S. Pat. No. RE37,615 andthe prior art listed therein. Typically subfloor layer 6 is formed of4′×8′ plywood panels and has a uniform thickness of about {fraction (1/2inch)}. The sleepers 2 typically have a cross-sectional height of about1.5 inch, and a width of about 2.5 inch, and a length of either 4 or 8feet. The sleepers are usually spaced apart about 12 inches, althoughthat spacing may vary depending upon their width. The foregoingdimensions are not critical, and hence sleepers having a differentheight, width, length and spacing may be used.

[0027] The pads 4 are molded from an elastomeric material in order toprovide resiliency, vibration dampening and shock absorption for thefloor system. The pads may take various shapes without affecting theinvention. Thus, for example, the pads may be as illustrated in U.S.Pat. No. 5,388,380, issued Feb. 14, 1995 to Michael W. Niese and U.S.Pat. No. 6,367,217, issued Apr. 9, 2002 to Michael W. Niese et al. Thepads may be solid or may be formed with hollow internal volumes orspaces to better permit the pads to deflect in the vertical directionimmediately upon impact to the hard wood floorboards 8. The pads aresized to provide a space of predetermined minimum height between thesleepers and the supporting base, typically a height in the range ofabout 0.5 to about 0.75 inch, under the static weight of the floorsystem.

[0028] Each sleeper member is provided with at least one and preferablytwo through bores 14 to accommodate fasteners 16 and standoff sleeves 18as hereinafter described. A counterbore 20 is coaxial with each bore onthe top side of the sleeper, so that each bore has a relatively smalldiameter bottom section and a relatively large diameter top section. Thebottom end of each counter bore has a flat annular surface 22 (FIG. 6).

[0029] According to this invention, the fasteners 16 are formed with ahead 24 having a conical side surface and a flat top surface and a shankthat has a pointed tip. Referring to FIGS. 4 and 6, preferably the shankis stepped so as to provide a relatively large diameter upper ortrailing section 26A and a relatively small diameter lower or leadingsection 26B, with a short tapered transition section 26C. By way ofexample but not limitation, the fastener may have an overall length of2.25 inch, a maximum head diameter of 0.5 inch, an overall shank lengthof 2 inches, a transition section (26C) length of {fraction(1/32)}-{fraction (1/16)} inch, and diameters of 0.200 inch and 0.190inch for shank sections 26A and 26B respectively. The larger diametersection 26A serves to provide column strength to the fastener so that itwill not buckle when it is impacted against the concrete base by thepowered driver as described hereinafter. The smaller diameter section26B and its pointed tip 27 facilitate piercing of the dense concrete;the tapered transition section facilitates penetration of the concreteby the leading end of shank section 26A. It is preferred, but notessential, that the shank section 26B have a plurality of shallowhelical grooves located rearwardly of the point tip section, asindicated at 28 in FIG. 6, to facilitate penetration of the denseconcrete under the impact force of a powered driver according to thisinvention. In order to assure penetration without bending, the fastenersare preferably made of an alloy or special high carbon steel and heattreated to HRc 53/56 hardness.

[0030] The standoff sleeves 18 may be made of various materials.Preferably they are made of a high density plastic such as Delrin® or ahigh impact plastic such as a high density polyethylene. The sleeveshave a cylindrical shape and are characterized by a center bore 30, anda peripheral flange 32 at one end, hereafter caller the top end.Additionally the top end of each sleeve has a conical countersink 34 forbore 30. The height of flange 32, i.e., its dimension measuredlongitudinally of the, sleeve, is less than the depth of thecounterbores 20. The overall length L1 of the sleeve is set so as to beless than the distance between the bottom surface 36 (FIG. 1) ofsubfloor 6 and the upper surface of base 8 after the floor system hasbeen anchored to the base without precompressing pads 4. Also the lengthof the portion of each sleeve between flange 32 and its bottom endsurface, represented as L2 in FIG. 6, is equal to the combined verticaldistance between the annular surface 22 of counterbore 20 and the uppersurface 9 of base 8 after the floor has been anchored to the basewithout precompressing pads 4. Sleeves 18 are formed with the diameterof center bore 30 equal to the diameter of shank portion 26B, so thatwhen the fastener is inserted into the sleeve, it will be held up byshank section 24A being gripped by surface-to-surface contact with thesleeve in bore 30 or by an interference fit between bore 30 and shanktransition section 26C, with the result that the head of the fastenerwill be in a raised or upwardly projecting position relative to the topend of the sleeve. Preferably the sleeve and fastener are sized so thatwhen the sleeve 18 is inserted in a hole 14 with its flange resting onthe bottom surface 22 of counterbore 20, and a fastener is inserted inthe sleeve, the head and a substantial portion of the shank portion 26Aof the fastener will project above the upper surface of the sleeper, asshown in FIG. 5. As a minimum, at least the head of the fastener shouldproject above the head of the sleeper in order to facilitate alignmentof the powered driver used to propel the fastener into a concrete base.Preferably also fastener 16 and sleeve 18 are sized so that when thefastener is inserted into sleeve its pointed tip 27 is even with, orjust short of being even with, the bottom end surface of the sleeve.

[0031] A suitable form of powered driver is disclosed in U.S. Pat. No.5,645,208, issued Jul. 8, 1997 to Harry M. Haytayan for “PneumaticFastening Tool With Safety Interlock”. The disclosure of that patent isincorporated herein by reference. With reference to the drawings of thatpatent, the driver illustrated therein includes a nozzle member 6 thatis provided with (1) an axially-extending bore 112 that accommodates ahammer 68 (also identified by persons skilled in the art as the“striker”), (2) a side entry port for fasteners carried in strip form bya magazine 8 that is attached to the nozzle member, and (3) a secondaxially-extending bore 118 that accommodates a spring-biasedvalve-actuating safety rod 120. Such a device is capable of drivingfasteners into concrete with a single impact without any predrilling,with the fasteners having a holding power in the concrete in excess of1000 lbs., partly as a result of the ball phenomenon described above.Pneumatic drivers embodying the design disclosed in U.S. Pat. No.5,645,208 are available commercially from Pneutek, Inc. of Hudson, N.H.One such driver is Pneutek Model PT 1100.

[0032]FIG. 7 illustrates a pneumatic driver 40 of the type disclosed inU.S. Pat. No. 5,645,208 and exemplified by Pneutek Model PT 1100, butmodified to incorporate a nozzle according to the requirements of thepresent invention. For the purposes of this invention, afastener-carrying magazine is not required. Consequently the nozzle doesnot have a side entry port for fasteners. The bottom end of nozzle 42has a circular configuration with an outside diameter that is smallerthan the diameter of the counterbores 20. Preferably the o.d. of thebottom end of the nozzle is about 0.19 inch less than the diameter ofcounterbores 20. Referring to FIG. 8, the nozzle has an axial bore 44for the striker or hammer (not shown) of the driver. Bore 44 is coaxialwith the center point of the nozzle's circular end face 46 and has adiameter that exceeds the maximum diameter of fastener head 24 by asmall amount, preferably by about {fraction (1/32)} to about {fraction(1/16)} inch. The nozzle has another axially extending bore 48 thataccommodates the safety rod 50 of the driver. Bore 48 is eccentric tothe center point of end face 46, being formed in a portion of the wallof the nozzle that surrounds bore 44. Rod 50 is biased downwardly by aspring 52 so that normally it projects beyond the end face 46 as shownin FIGS. 7 and 8. Rod 50 is equivalent to and serves the same functionas the safety rod 120 disclosed in the aforesaid patent.

[0033] Still referring to FIGS. 7 and 8, the bottom end of the nozzle isprovided with a circular recess 56 that is coaxial with bore 44. Recess56 functions as a counterbore for bore 44. The annular surface 58 thatforms the inner end of recess 56 is flat. Recess 56 has a diameter thatis slightly greater than the o.d. of flange 32 of sleeves 18, preferablyabout {fraction (1/32)} to about {fraction (1/16)} inch greater.Preferably the depth of recess 56, i.e., the dimension measured parallelto bore 44, is the same as that of flange 32, but it may differtherefrom by a small amount, e.g., plus or minus {fraction (1/32)} to{fraction (1/16)} inch. As noted above, the diameter of striker bore 44must be large enough to readily accommodate the fastener head 24 but notso large as to introduce a degree of lateral play that make itsdifficult to locate the nozzle in a counterbore 20 or will locate thestriker axis off center with respect to the fastener head. The length ofthe striker (not shown) is set so that when the driver is fired, i.e.,operated, the striker will move through its downward stroke far enoughto cause the end of the striker to be flush with or protrude beyondannular surface 58 of nozzle recess 56 by approximately {fraction(1/32)} inch, whereby to cause the head of the fastener to be seated incountersink 34 and to force the sleeve into tight engagement with base8.

[0034] With the foregoing apparatus, anchoring of floor systems of thetype described in U.S. Pat. No. RE37,615 is greatly facilitated. Toanchor a sleeper as herein described and illustrated, a sleeve 18 and afastener 16 are inserted in one of the holes 14 (FIG. 5). Holes 14 andsleeves 18 are sized so that holes 14 are approximately {fraction(1/32)}″ to approximately {fraction (1/16)}″ larger than the o.d. of thesleeves. The sleeve may be inserted first, followed by the fastener;alternatively and preferably, a fastener 16 and a sleeve 18 areassembled together as shown in FIG. 5 and then inserted into a hole 14.In either case, the bottom end of the sleeve will touch the uppersurface 9 of base 8 and the bottom side of flange 32 will engage ornearly engage the surface 22 of the sleeper. Then nozzle 42 of driver 40is placed over the sleeper so that the head of the fastener extends upinto striker bore 44 and flange 32 of sleeve 18 resides in recess 56.When the bottom surface 46 of the nozzle engages the upper surface offlange 32, safety rod 50 will be depressed, activating the driver foroperation by the user. With the driver connected to a source ofpressurized air, the driver is fired by squeezing its trigger 60. Whenthe driver is fired, the striker of the driver will impact the head ofthe fastener at a high velocity and with a great downward force, causingthe fastener to penetrate concrete base 8. The striker of the driverforces the fastener into the concrete far enough (approximately 1″ to1½″) to cause its head 24 to be seated in countersink 34 and to locksleeve 18 tight against the base 8. However, because of thedepth-limiting action of the sleeve on the fastener, the fastener is notdriven into the concrete so far as to precompress the resilient pads.Further assurance that the fasteners are driven into the concrete thecorrect amount is provided by the fact that the stroke of the striker islimited as described above. The limited stroke of the striker alsoeliminates any possibility that the striker will crush the sleeve.

[0035]FIG. 6 also illustrates a preferred relationship of fastener head24 and counterbore 34. Although satisfactory results are obtained whenthe angle of taper of the side surface of the fastener head 24 is thesame as that of countersink 34 of sleeve 18, it is preferred that thetaper angle of the countersink be less than that of the fastener headmeasured relative to the center axes of the sleeve and fastener.Preferably the countersink has a taper angle of about 60° and the sidesurface of the fastener has a taper angle of about 82°, as indicated inFIG. 4. The advantage of that arrangement is explained with reference toFIG. 6 which illustrates the position of the fastener as its head firstengages the sleeve under the driving force of the striker of driver 40.The first contact between fastener head 24 and the countersink surface34 is limited, consisting essentially of a circumferential line contactwith the force of the fastener head comprising both radial and axialvectors. As the fastener is driven further down into the sleeve, itshead deforms the countersink portion of the sleeve radially so as topermit the entire inclined side surface of the head to contact thecountersink surface. Essentially the area of contact between thefastener head and the sleeve increases with increasing penetration ofthe fastener. The difference in taper angle limits the initial contactarea and also allows the fastener to move down vertically relative tothe sleeve at the beginning of the stroke, thereby limiting themagnitude of the initial shock of impact experienced by the sleeve andconsequently reducing the possibility of the sleeve being shattered bythe initial impact. This is an important consideration in the case ofhard plastic sleeves, since fracture of the sleeve will frustrate therequirement that the compressible pads not be preloaded.

[0036] The invention is not limited in its application to floor systemsof the type wherein the floor attachment members are in the form ornailing strips or sleepers that carry the resilient pads. Thus, forexample, the invention also is applicable to a hardwood floor system ofthe type disclosed in U.S. Pat. No. 6,367,217, issued Apr. 9, 2002 toMichael W. Niese et al. for “Sleeper Assembly For Resilient HardwoodFloor System”. FIG. 9 illustrates that system. In this case the systemcomprises an upper floor wear surface in the form of a plurality ofinterlocked floorboards 60 supported in spaced relation to the densesupporting base 62 by spaced rows of substructure assemblies 64. Eachsubstructure assembly comprises an elongated panel 66, a pair of spacedrows of compressible pads 68 attached to the bottom surface 70 of thepanel adjacent its opposite edges, and corresponding pair of rows ofnailing strips 72 secured to the top surface 74 of the panel above therows of pads. The floorboards are nailed to the substructure assembliesand the latter are secured to the base by fasteners 76 that pass throughholes in the panels and are secured in holes in base 62. Each fasteneris provided with a shoulder 78 intermediate its opposite ends thatfunctions as a depth stop to limit the depth of fastener penetrationinto the base and thereby prevents precompression of pads 68 by thedownward driving forces applied by the fasteners as they are driven intothe base, with pre-drilled holes being required in the case of aconcrete base. A lubricating sleeve 80 is disposed in each of the holesin panel 66 in surrounding relation to the fasteners and has a flange 82that overlies panel 66. The head 84 of fastener 76 is seated againstflange 82. The sleeves project down through panel 66 only a limiteddistance and do not contact the base when the fastener is driven intothe base to the extent allowed by depth stop 78. The nailing strips 72provide an air space 86 between the upper surface 74 of panel 66 and thelower surface 88 of floorboards 60.

[0037] Since substructure assemblies of the type shown in U.S. Pat. No.6,367,217 are installed first before the floorboards 60 are nailed inplace, the present invention makes it possible to anchor them to a hardconcrete base without any need for predrilling holes in the base. Thisis accomplished by replacing fasteners 76 and lubrication sleeves 80with fasteners 16 and sleeves 18 as illustrated in FIGS. 1 to 6, withthe lengths of the fasteners 16 and 18 being adjusted to allow thesleeves to function as depth stops and the fasteners to penetrate thebase to a depth sufficient to assure that the heads of the fastenerswill force the sleeves into tight engagement with the base withoutprecompressing the resilient pads. As with the sleeper type constructionshown in FIG. 1, the sleeves 18 and the holes in each panel 66 are sizedso as to provide a clearance of approximately {fraction (1/32)}″ to{fraction (1/16)}″. In both types of floor constructions, the reason forsuch clearance is to prevent floor squeaking as the floor is subjectedto loading and unloading forces.

[0038] Although it is preferred to use fasteners with step-down shanksas shown in FIGS. 4-6, the invention may be practiced with fastenersthat have straight shanks, e.g., a shank having a substantially constantdiameter except for a pointed leading end. In such case it is preferredthat the shank diameter be the same as that of bore 30 so that the shankmakes a tight fit in and is gripped by the sleeve. Also, it is preferredthat the fastener and sleeve be pre-assembled with the pointed tip ofthe fastener substantially even with the bottom end of the sleeve.Alternatively, the shank diameter may be slightly smaller than bore 30,in which case the sleeve 18 may be inserted in hole 14 first, and thenthe fastener may be inserted into bore 30 with its tip engaging theunderlying base 8.

[0039] As used herein in relation to resilient support pads 4, the terms“precompressing” and “precompression” are synonymous with “preloading”and are intended to embrace the situation where the pads are essentiallynot compressed at all by the fasteners, and also the situation where thepads are compressed somewhat as a consequent of the fastening operationbut are still capable of further compression to the extent required toallow the floor system to deflect downwardly when impacted within theoperating limits contemplated by the parameters of the system. In thiscontext it is recognized that the support pads 4 and 68 are compressedby the weight of the floor components, and such compression is not to beconstrued as coming within the scope of the term “precompression”.

[0040] The advantages of the invention are obvious and significant. Nopredrilling of the concrete base is required in order to anchor floorsystems with fasteners. Furthermore the invention eliminates the need touse fasteners characterized by a shoulder that functions as a depth stopand fasteners having expansion curves for locking them in pre-drilledholes in a concrete base. The driving of the fasteners is rapid, withthe manual labor limited to inserting the sleeves and fasteners in holesin the wooden attachment strips, and positioning and firing the driver.Additionally pneumatic drivers of the type described herein are reliableand easy to use, and a nozzle as shown in FIG. 8 is capable ofwithstanding the wear and tear encountered in the field. Overall theinvention provides a tremendous saving of cost and time while providinganchor strengths far in excess of what has been achieved heretofore inthe installation of hardwood floor systems on concrete slabs. Stillother advantages will be evident to persons skilled in the art.Moreover, those skilled in the art will readily comprehend the variousmodifications to which the invention is susceptible.

What is claimed is:
 1. Method for anchoring to a concrete base anattachment assembly for a wood floor wherein said attachment assemblycomprises an attachment member that has top and bottom surfaces andhaving at least two holes each with a counterbore extending down fromsaid top surface, and at least two compressible pads each having a topside and a bottom side with said top side contacting said lower surfaceof said attachment member, said method comprising the following steps:(1) inserting (a) a sleeve having center bore, a distal end, a proximalend and a peripheral flange at said proximal end into each of said holesso that said peripheral flange resides in said counterbore and (b) afastener having a distal end and a proximal end with an enlargeddiameter head at said proximal end into each of said sleeves, with saiddistal end of said sleeve projecting below said attachment member by apredetermined amount so that it is substantially flush with the bottomside of said each compressible pad and with said head of said fastenerextending above said proximal end of said sleeve; (2) providing amanually operable pneumatic driver having a nozzle with an end surfacethat is sized to fit in said counterbore, a striker mounted for axialmovement in a striker bore in said nozzle with said striker bore havinga diameter at least equal to the diameter of said head of said fastener,and means for reciprocally driving said striker through (a) a rapiddrive stroke whereby said striker is moved from an at-rest position inwhich the striker is withdrawn into said bore to an extendedfastener-driving position in which said striker projects beyond said endsurface and (b) a rapid return stroke whereby the striker is withdrawnfrom said fastener-driving position back to said at-rest position; (3)positioning said driver so that said end surface of said nozzle resideswithin said counterbore and so that said fastener head resides in saidbore; and (4) operating said driver so as to cause said striker toimpact said fastener head with a force sufficient to drive said fastenerinto said base far enough to cause the head of said fastener to (a)drive said flange into tight engagement with said attachment member and(b) force said sleeve into tight engagement with said base.
 2. Methodaccording to claim 1 wherein in step (1) the head of said fastenerextends above said attachment member.
 3. Method according to claim 1wherein in step (4) the depth of penetration of said fastener into saidbase is limited by said sleeve.
 4. Method according to claim 1 whereinsaid distal end of said fastener is substantially flush with said distalend of said sleeve prior to step
 3. 5. Method according to claim 1wherein said sleeve has a tapered countersink for said bore at saidproximal end, and said fastener head has a conical side surface. 6.Method according to claim 5 wherein the angle of taper of said fasteneris greater than the angle of taper of said countersink.
 7. Methodaccording to claim 6 wherein said countersink has a taper angle of about60° and said conical side surface has a taper angle of about 82°.
 8. Afastener/standoff sleeve assembly for use in anchoring an attachmentassembly for a wood floor to a concrete base, said assembly comprising:a fastener having a shank with a distal end and a proximal end, apointed tip at said distal end, and an enlarged diameter head at saidproximal end, with said head having a side surface that is taperedinwardly; and a sleeve for positioning said fastener in a hole in saidattachment assembly, said sleeve having a distal end, a proximal end, acentral bore that extends between said distal and proximal ends foraccommodating the distal end of said shank, and a tapered countersinkfor said bore at said distal end of said sleeve, said countersink beingshaped to accommodate said head of said fastener when said fastener isdriven into said sleeve by an impact on said head while said sleeve isimmobilized against axial movement.
 9. A fastener/standoff sleeveassembly according to claim 8 wherein said fastener head has a conicalside surface that has a taper angle greater than the angle of taper ofsaid countersink.
 10. A fastener/standoff sleeve assembly according toclaim 8 wherein said fastener shank has a proximal relatively largediameter portion and a distal relatively small diameter portion, andsaid hole is sized to accommodate said distal relatively small diameterportion but not said proximal relatively large diameter portion. 11.Method for anchoring to a concrete base a floor attachment assembly thatcomprises a floor attachment member having top and bottom sides, atleast two compressible pads attached to the bottom side of said floorattachment member, and two holes extending through said attachmentmember, said method comprising the following steps: (1) providing afastener and sleeve assembly that includes a fastener having a shankwith a leading end and a trailing end and a radially-projecting head atsaid trailing end, and a sleeve having an axial bore, a bottom end and atop end with a radially projecting flange at said top end, said leadingend of said shank intruding into said axial bore; (2) inserting saidfastener and sleeve assembly into said one of said holes with saidbottom end of said sleeve projecting below the bottom side of saidattachment member and with the head of said fastener disposed above andspaced from the top side of said attachment member; and (3) impactingsaid fastener head with a pneumatically-powered hammer with sufficientforce to drive said fastener into said concrete base far enough to causethe head of said fastener to (a) force said flange into tight engagementwith said attachment member and (b) anchor said attachment member tosaid base without compressing said pads.
 12. Method according to claim11 wherein in step (1) the head of said fastener extends above saidattachment member.
 13. Method according to claim 11 wherein in step (3)the depth of penetration of said fastener into said base is limited bysaid sleeve.
 14. Method according to claim 11 wherein said sleeve has atapered countersink for said axial bore at said proximal end, and saidfastener head has a conical side surface.
 15. A fastener/standoff sleeveassembly according to claim 8 wherein said sleeve has a peripheralflange at its said proximal end.
 16. A fastener/standoff sleeve assemblyaccording to claim 8 wherein said fastener has it shank inserted intosaid central bore of said sleeve, with said enlarged diameter head andthe portion of said shank adjacent said head projecting from saidproximal end of said sleeve.
 17. A fastener/standoff sleeve assemblyaccording to claim 16 wherein said fastener shank is gripped by saidsleeve.
 18. A fastener/standoff sleeve assembly according to claim 16wherein said tip is substantially flush with said distal end of saidsleeve.
 19. A fastener/standoff sleeve assembly according to claim 18wherein said sleeve has a peripheral flange at its said distal end andsaid enlarged diameter head of said fastener is spaced from said flange.20. A fastener/standoff sleeve assembly according to claim 8 whereinsaid distal end of said sleeve has an end surface, said shank is steppedwith a relatively large diameter portion extending distally from saidhead and a relatively small diameter portion extending between said tipand said relatively large diameter portion, and said relatively smalldiameter portion is disposed in said bore with said tip beingsubstantially even with said end surface.